The invention discloses a software authentication method based on a softdog, comprising the following steps: binding software and the softdog; detecting whether the softdog bound with the software is accessed or not when the software is started each time, if not, denying access, and if so, detecting whether the user mode of the softdog is a used mode or not, if the user mode of the softdog is not the used mode, marking the used state in the softdog and allowing access, if the user mode is a used mode, detecting whether an authorization message can be acquired from the host of operating software, if the authorization message can be acquired, allowing access, and otherwise denying access. By the invention, the fact that one softdog can be utilized on only one host can be ensured, thus effectively preventing the copy propagation behavior of a user possessing the softdog and protected documents, and improving the safety of software authentication.